ABSTRACT Kidney disease in the United States has been described as an epidemic. More than 20 million patients have chronic kidney disease (CKD) and these numbers are increasing annually. As a result, the number of patients with end-stage renal disease (ESRD) is expected to double between 1999 and 2010. These increases in CKD and ESRD are associated with significant morbidity, mortality and healthcare costs. Early detection and treatment of kidney disease has been shown to improve outcomes, but kidney disease is often under diagnosed resulting in lost opportunities to treat. The importance of early diagnosis and treatment of kidney disease has been extensively reviewed and published as a K/DOQI clinical practice guideline by the National Kidney Foundation. Monitoring changes in glomerular filtration rate (GFR) provides the best means for early detection of kidney disease. The test that is most widely used in the US to screen abnormalities in GFR is serum creatinine. However, estimated GFR values using serum creatinine have limited diagnostic value over methods that directly measured GFR using an ideal filtration marker, such as inulin. This Phase I application seeks support to further develop a novel readout system, based on immunoassay technology, to directly measure GFR. Our proposed test will be accurate, simple-to-use, inexpensive and will be widely assessable. The test will utilize FDA-cleared compounds that are known to be GFR markers. As a result, our proposed GFR test will be able to more quickly enter the marketplace.